Spark plug and method of making same



Allg 2651941. J. H. DILLoN f .2,254,169 SPARK PLUG AND METHOD-0F MAKING sum i Filed Dec. 29. 1939 5 Y n v m A v A'ronuevs.

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gested for the purpose of -improving the opera@ tion of the spark vplug-ass radioactive'material causes ionization of the molecules of gas in the .gap by means of the rays orparticles emitted,

whereby a spark can traverse the vgap ata lower;

"electric voltage than with no radioactive sub- 'stance' present.

However,l previously known types of radioactive spark piugg are not entirely commercially satisfactory, for some uses because they are either too expensive end dangerous (when a radium compound'is used). or ineffective (when uranium o r thorium compoundsare used). These and other diiiiculties have pre- `vented the production of commerciallypractical radioactivespark plugs. I 'he present invention is, in part, anlimprovement on the radioactive spa'rk plug disclosed in U. S. `Patent`tjiumber 1,723,422', t0 A. M. Hubbard'.

The general object of the invention is -to pro- [vide a commercially satisfactory radioactive electrical discharge device comprising a chemically unco'mbined strongly radioactive metal, and a method ofmaking the discharge device.

aAnother object of the present invention is to provide' a spark plug for internall combustion engines embodyingfpoloniumat or near the spark gap, and a-rnethod/of making1ame. Another object 'is'to Vprovide'an electrical discharge deviceincluding a strongly radioactive metal at or near the gaseous discharge region `whereby an electrical discharge may be made to f transverse the' region' Vat a lower voltage than that required in previously known constructions.

Another object lis toV provide a combustion Vchamber for an internal ycombustion engine in which a strongly radioactive metal is so situated that ions producedby itsrays enter` the gap of the spark plug. v

v 4 comprising polonium, whereby quicker starting, smoother operation, greater power, and increased A further 'object 1s' toprovide a spare p'xugg fuel economy are obtainedin an eggine emply ing Such-'Spark plugs.r f

l Other obiects will bemanifest as the specificay.

l vtion proceeds,

f Referringto the drawing: -Figure lis an elevation vcfa spark plug insulator and accompanying cen- (el. 12a-169) bodym; the invenumror use in an internal combustiony engine;

Figure 2 is a -fragmentary enlarged elevation.;

of aspark plug groundei'ectrodev modiiiedac- '.5 cording to one embodiment of the invention;`

Figure 3 is a fragmentary enlarged elevation of a spark plug center electrode modified according to another'embodiment of thel invention;

"other embodiment. of the invention;

Figure 5 is a fragmentary elevation of the lower end of a spark plug'modied Vaccordingto an' f' other embodimentof the invention; l Figure 6 isa fragmentary sectional elevation ter electrode modified according to bodiment of the invention;

Figure 'l is a fragmentary 'enlarged'viewof a ,meer em- 'ground electrode `modiiied'according' to'another embodiment ofthe invention; `Figure 8 is a fragmentaryr enlarged'view of 'a embodiment of the invention; and f Figure 9 is adimin'ished sectional view-cfa combustion chamber of an internal combustion engine, modiiied in accordance with'a further embodiment of 'the invention.

Broadly speaking, the

discharge may be causedl to. traverse the disthe ionized 'gas type represent onelform of,r such Luminous'gas tubes, such as neon sign-lamps. represent another form Vof such device. The ordinary spark`plug` `used in gasoline engines Aconstitutes yet'anothei-form of such device. It 45 will be understood that the various modications r described below for a spark plugmay also/be applied to other v'electrical discharge devices,y

where suitable,"

All'radioactlve materials give oifone or more 50 of three types 'of ionizing rays called-alpha,l beta. -f and gammarays.' The alpha rays; whicharerDidly. xno ving.' d doubly-charged particles, are.

lnuch more eiiicient ionizers than either e beta rays (fast electrons) or gamma rays (e eccfa spark plug em- 55 4tromagnetic radiation of extremely; highL/fre-j ground electrode modied according to a furtherA resent -invention con' templates providing an electrical discharge de vice 'ivhich contains achemically uncombined strongly radioactive metaL'Whereby an-electrical charge region of the device 'at a lower voltage than with standard constructions. Usuallyfgthe radioactive metal is so positioned that its ionized field embraces said discharge region.` Relays 'of' electrical discharge device, an example being a 40 cold discharge -tubeot thef'Grid-Glow type.

Figure 411s a fragmentary enlarged elevation 1o of a ground electrode modiiied according to an quency). Furthermore, the alpha rays are not dangerous vto human beings.' whereas gamma rays may be exceedingly harmful and require extreme safety precautions. 'I'hefbeta rays also are dangerous to some extent. Hence, it is quite apparent that a radioactive material emitting determinations. (See E. Walling, Zeitschrift fr Physik, 87, 603 (1934) Table I Atomic Half liIe Radiation Wt. No.

258 .92 4.67Xl'yrsm Alpha. 234 90 24.6 days Beta. 234 91 1.15 min Bcta (gamma). 234 92 2x10* yrs lpha. 230 90 45.9Xl04 yrs Do. 226 88 1690 yr Alpha (beta and gamm 222 86 3.85 days Alpha. 218 S4 3.0 min. Do. 214 82 26.8 min Beta (gamma). 214 83 19.5 min... Betaandgamma. 214 8i l0iscc Alpha. 210 82 22.3yrs (Beta and gamma). 210 83 5.0 days Beta. Radium F or Po- 210 84 136 days Alpha (gamma). lonlum. Radium Omega or 206 82 Lead.

( means radiation is relatively feeble.

Of the alpha ray'emitting elements shown in Table I, onlypOlonium and its transformation product emit substantially no beta or gamma rays. Although radium emits only feeble Abeta 10 rium-,'protoactinium, radioactinium and actinium for use in the present invention for the reasons given above, other radioactive substances may sometimes be used inthe practice of the invention even though such substances do not have as desirable characteristics as polonium. Certain other strongly radioactive metals emit alpha rays l at effective rates and have sufdciently longl life periods to render them useful in spark plugs. Such other useful metals are radium, radiotho- X. It would be necessary to handle devices containing one of these metals with proper precautions in view-of the beta and gamma radiation attending the desired alpha rayv emission. A

metal having an induced radioactivity of a strong character, equivalent to the activity of polonium and the other strongly radioactive metals named above, is also contemplated for use in the present invention.

While poloniuml usually may be used for the purposes of the invention in any form desired, such as the pure elemental metal, as a plate upon :another surface, or' as an alloy with one or more other metals, it is alloyed polonium that has'been found most convenient for general use in discharge devices. Polonium alloy is preferably prepared by iirst plating a thin layer of polonium on metallic foil and then adding the required amount of the plated foil to a melt como prising the bulk ofthe non-radioactive components of the alloy. 'I'he mixture ofmetals is l maintained fluid for a Sumcient length .of time hundred thousandth of one per cent 'to one biland gamma rays, certain of its products (radium B, C and E) emit strong beta and gamma rays. It is well known that polonium emits only a few quanta of gamma rays for each million alpha rays. (See H. C. Webster, Chemical Abstracts, 32, 1565-6 (1938).) Practically speaking, therefore, polonium emits only alpha rays.

In selectingthe proper radioactive material for use, another factor must be considered. All radioactive elements change into other elements according to an exponential law governed by their activity (number of rays per second). The selection of a radioactive material such as uranium, for example, would be unwise, because -even though it has a half-life (time required for one mass unit of the substance to bereduced to onehalf mam unit) of approximately ilve (5) billion years and emits only the desirable alpha rays. its activity is so low that several grams would be required to give a definite improvement in a single spark plug, whereas the weight of the ordinary side wire electrode is considerably less than one gram..V On the otherl hand, radium Aemits only alpha rays very copiously but has a-hali'flife of 'only 3 minutes. Polonium Aemits alpha rays at a rate in excess of 4500 .times the alpha emission rate :of pure radium and has the reasonable halflife period of 136 days. n These properties, in addition to the property of emitting substantially no beta or gamma rays, constitute polonium as an ideal substance for use in a radioactive spark plug, and the invention will be vdescribed with reference y to polonillmpas'used inra spark plug.

lionth of one per cent is preferred for the preparation of spark plug electrodes of th'e kind hereinafter described. Such alloy is readily swaged and drawn into wire form by conventional methods, since it is identical in ordinary physical properties with conventional spark plug alloy, diil'ering from the latter only inV radioactivity. 'Ihe method -tust described for preparing a polonium ,50 alloy may be applied to the production of alloys comprising other strongly radioactive metals, such as those mentioned in the preceding paragraph. If a plated electrode is desired. the base electrode is made and suitably prepared to receive the plated material as by plating a thin film oi' nickel thereon. Then the polonium can'be deposited chemically orelectrolytically upon the base metal. Of course, any elementaLpolonium member used in practice of the inventiony can be suitably formed from the uncombined material.

In Figure 1 of the drawing, a spark plug Il of 'v standard construction is shown. This spark plug i includes a porcelain insulator I I, mounting a center electrode I2 thereimand a metal shell Il, in which the insulator II is received, that carries a cylindrical ground' electrode 4Il. Preferably the ground electrode I4 ismadefrom an'alloy com,

:prising polonium andordinaryspark'` plug wire metal. Thecenter'electrode I2 may also be milde from the foregoing alloy, it desired, or in some maybe made from .luthough polonium is the preferred substance alloy. may be welded tothe groundelectrode, as

inli'lgurewm y A.

According to` a further embodiment of the invention, a smallpiece-of polonium orpolonium al- Since an important feature of the invention re` loy il maybelusedon to thegroundelectrodaas .l n. etais-.ff, v-

s in ll'igurcimrtothe'centerelectrode,satIl"y were required Aior when the ,plugswereused s interesting .discoveryhas been made whichv further emphasizes the practicar-tenente :tube

derived Afrom the use o! spark plugs containingv i polonium'. When a spark plug containing' polonium in one or more oi theelectrode terminals l sides in" positioning some, form of polonium near has been used fno'ratime in an internal ycombusthe lectrode gapv of a fsparkplug to-aid in ioniz tion engine.it is even more eilicient in operation l ing the gap. it is seen thatf this polonium can be ,10 than an unused plug of the same type which con- 'positioned there -in numerous ways. Figure 5' Y V tains about the same amount or polonium. v. A f

' shows the lower end of ya spark plug shell Il which has an auxiliary wire'f20 carried thereby and extending therefrom, which wire includesy polonium. Figure 6 illustrates an embodiment of the. invention wherein a shortpiece lof electrode wire I-'I having polonium'associated therewith is welded, or otherwise secured toa center electrode :|25 at the -lower endv thereof. y'll'his wire i1 may f l extendinto the'insulator lib, as shown. In some l '.instancea it may be possible to aillx thepolonium.- or polonium bearing element to. the spark plugin a manner dii'ierent from that shown in Figures F 5 and6 and-still have it ionize the electrode gap:

inthefdesiredmanner. f u v v yA modiiled ground electrode I is shown in.

Figure"1. This electrode -is of right angular shape'and of rectangular, or square cross-section. Acircularf section electrode v`l 4d, which has 4 .a planar face ilfto bepositioned opposite the center electrode with which it is associated, is -illustrated in Figure 8. .'These"electrodes usually are made from a polonium containing alloy metal. The eiiect of polonium in a spark plug maybe explained as follows:

When 'the coil voltage 'is appliedto the plug -by means ofthedistributor, 'a very short interval of time elapses before the voltage reaches a value atwhichvthe spark gap breaks down. Ii' a large number o vin varying numbers, happen `to be in the gap at the time'the voltage is applied, the gap will break down very soon after the beginning of the volta-ge 'rise 4and at a reasonahly low voltage. However, if. ,s the natural ions` are notvplJentlful', the` spark will \not.occur so promptly'afte'r the beginning of the voltage rise and the eifective breakdown voltage wm behigher. A In other words, the plug vrequires a. higher excess voltage underthese conditions. A which conditions are common lwith plugs o! the conventional type. A-partially discharged batftery.' a defective-spark coil or extreme cold often Y prevents" the largevoltage'rise necessary for lsatisfactory operation of conventional spark plugs.

Frequently, conditions will be so unfavorable that a spark will not occur at all, and it will be neces` sary to turn the engineover a number of times fi natural ions. which are always present 4 possible explanation of this gratifying phenometration of polonium on the surfaceof the terminal. Or, the `enhanced eiciencymay be due to 'Y 'I the combinationof alpha rays/emitted by polonium in.the ovide layer and'those emitted bythe polonium in the underlying metal, the latter rays 20 easily penetrating' the porousv coating. 'Moreoven it may be possible that polonium becomes con--v .centratedfonthe' outer surface of the oxide coatf- Polonium has 'an important secondary'eiiect in the combustion' chamber ofaninternalecombusy tion engine. When an vemitted alpharay strikes a hydrocarbon molecule or'y an oxygen molecule in the combustion mixture, themolecule. becomes4 j f ionizedor activated so that it will enten-'into a.-

new chemical combination more readily. By vir' tue of this activating eiiect; smoother operation and increased gasoline economy result when polonium-containing spark plugs are used4 in such" 'I an engine.

As a resultof many other practical/tests made Y, on the polonium-containing spark plugs, it has been proved that' such plugsfefiectbetter starting y of the engine under all conditionssmoother'op'- eration of the engine, less choking required with'a cool engine (and hence, a considerable saving in fuel)A and increased power on hills. Other'tests have" shown that polonium gives even a greater" advantage in plugs that have been run several thousand miles in hard service than in new plugs.

Otherwise'stated, polonium tends to preserve the d 'good 'initial propertiesy of the (spark plug after thousands of miles of hard service.

The. development of a`practical 'radioactive spark plug is important. not. only in improving the operation vof presentinternal combustionI en; gines, but alsoirr allowing the development and '-f utilization of engines having higher compresl sion fratios. `Development ofengines in this di rection has been seriously 'hampered by the in- Iability of conventional spark plugs to operate.`

reliably at high pressures.- At high pressures the spark gap' breaksdown vwith much greater diftl' f before a spark occurs. However, if Athe alpha rays y U muy than at lowbmssures because .of the greater Lof polonium are passing through the "gap, a large .insulating quality pf the.' increased' amount f vnumber ofextaions are formedvby each alpha 60 sus in the gap' Howeverif alpha' rays from a' ray (10.000 ions Desealpha ray) and 'the gap 'i Smtable imdwactive substafn such afs pokmum' breaks down promptly after the voltage begins. to are pass ng through the gap many carre-rincon; ducting ions are formed .and the gapbreaksl ris'eand at a lower voltage value than that'redown on the buildin Y f y s I g up of the usual electric i qumd by Standard s Park Plugsf Thus it might 65' voltage onthe* spark plug to allow a spark to` be said that polonium creates-favorable condimueven-t very high pressmF-ey l Ths, th

characteristics of -many 'polonium-'containing spark plugs with ordinary 'spark plugs, all plugs i having hadmor'e than a 'year of hard service, inv

Yimproved spark plug -of the vpresent invention will eiect' further economies for the motorist by allowing him to take advantagev of amore ef- `-m cient; veryhigh compression engine.

In .a furtherembodlment of th h "present in'- vention. the polonium may ieven be associatedwith thecombustion chamber of a .gasoline `en' -1 several engines .at ,-1-15 F. It was found that gine. That'is; polonium could be alloyed withfa" thirty ieper cent f ewenrevolutions of'an engine 7.5 vportion of the member deilning the chamber, or

a piece of polonium could be welded `or otherwise secured in the chamber in any desired manner. One embodiment of this feature of the invention isillustrated by Figure 9, wherein a spark plug 2l. of conventional design. is shown mounted in anengine cylinder head 22, defining the upper limits of acombustion chamber. The lower limits of the chamber are deiined by the engine block 23, valves 2l. and. a piston 25. Shown mounted on the inner surface of the cylinder head 22 is a member 2having radioactive metal. such as polonium. associated therewith, and attached to the cylinderhead by a suitable means. such as a screw 21. 'I'he member 20 is so positioned inV the chamber that ions produced -by rays from the radioactive metaL,

associated with the membenare present in the discharge gap of the spark plug 2|.

aas-inea ing into said chamber. the gap between said electrodes having ions therein produced by rays from said polonium-containing member.

8. A spark plug for an internal combustion engine, saidI spark plug comprising a pair of opposing electrodes, and a Vmember including a chemically uncombined, strongly radioactive metal. the gap between said electrodes being embraced by the ionized eld of said radioactive metal.

9. A spark plug for an internal combustion engine comprising a pair of opposing electrodes, at

It is'to be understood in 'the appended claims that a radioactive metal is chemically uncombined when it occurs as the pure elemental metal. as a iilm plated onto another substance, or as a component of an alloy. Although it is thought that the radioactivealloy utilized in the present invention is a4 substantially uniform dispersion of the chemically uncombined radioactive metal throughout the other componentsof the alloy,

l it is vpossible that `some of-the radioactive metal 'is oxidized during the alloying process, so that the alloy may contain a substantially uniform dispersion of the oxidized radioactive metal.

It is obvious thatvarious changes and modifl- I cations may be made in the above description without departing fromv the nature and spirit of the invention.

What is claimed is:

1. An electrical discharge device comprising a pair of opposing electrodes having a gaseous discharge region therebetween. and a memberincluding a chemically uncombined, strongly radioactive metal, said discharge region being embraced by the ionized eld of said radioactive f metal.

` 2. An electrical discharge device comprising a pair of opposing electrodes having a gaseous discharge region therebetween, at least one of said electrodes having associated therewith a chemically uncombined strongly radioactive metal.

3. An electrical discharge device comprisingl a pair of opposing electrodes having a gaseous discharge region therebetween andassociated therewith an alloy of a strongly radioactive metal, said discharge region having' ions therein produced by rays from said alloy.

4. An electrical discharge device comprisinga pair of opposing electrodes vhaving a gaseous discharge region therebetween and a chemically uncombined, strong-ly radioactive metalassociated therewith. 1

'5. An electrical discharge device comprising a pair of opposing electrodes having a gaseous dis charge region therebetween, at least one of said electrodes having polonium associated therewith.

8. In an internal combustion engine, a combustion chamber, a pair of opposing spark plug `least one of said electrodes including a chemically uncomined, strongly radioactive metal.

10. A spark4 plug for'a'n internal combustion engine, said plug comprising a polonium-containing member, and a pair of opposing electrodes, the gap between said electrodes being embraced by the ionized eld of said polonium. 1l.A spark plug 'for an internal combustion engine. said plug comprising a pair of opposing electrodes, an outer shell carrying one of said electrodes, and a'polonium-containing member positioned on said'shell, the spark gap between said electrodes being embraced by the ionized eld of said polonium.

12. A spark plug for an internal combustion engine, said spark vplug comprising a pair of opposing electrodes, at least one of said electrodes including polonium.

13. A spark plug for an/ internal combustion engine, said plug comprising' a pair of opposing.

electrodes, at least one of said electrodesV being composed of'an alloy comprising polonium.

14. A spark plug for an internal combustion engine, said spark plug comprising a pair of opposing metal electrodes, one of said electrodes having a strongly radioactive metal substantiallyuniformly dispersed therein.

15. In a spark plug,vtwo electrode elements, i the end portions of which are positioned in closely spaced right angular relation, one yof said elements comprising a polonium alloy Vand one of said elements having a planar side portion positioned adjacent the end of the second oi' said elements.

,16. A spark plug for an internal combustion engine, said spark plug comprising a pair of opthe resulting mixture molten until a homogeneposing electrodes, one of said electrodes being made of a polonium alloy in which between one-one hundred thousandth of one per cent and one-billionth of one per cent polonium is present.

\ c 17. In a process of making a radioactive spark plug, the steps of plating a strongly radioactive metal on the surface of' a metal, adding the plated metal to molten metal and maintaining ous radioactive alloy is produced. cooling the alloy to solidify it, forming same into an elecplug, the steps of plating a strongly radioactive electrodes extending linterina chamber, and smember, including a chemically uncombined strongly radioactive metal, associated with said chamber, the gap between electrodes having ions therein produced by rays from said member.

'1. In an internal combustion engine, a combustion chamber having a polonium-containing lmember associated therewith, and a pair of spaced but opposed spark plug electrodes extendtrode, and incorporating the radioactive electrode in a spark plug.

18. In a process of making a radioactive spark metal on the surface of a metal, addinglthe plated metal to molten metal and maintaining the resulting mixture molten until a homogeneous radioactive alloy is produced, coolingthe alloy to solidify it, and forming same into an electrode.

19. An electrical discharge device comprlsing'a I metallic electrode having associated vtherewith a chemically uncombined strongly radioactive metal.

-20. An electrical discharge device comprising '4 v v throughs. gaseous medium, said electrode havingl a metallic electrsde having associated therewith an alloyy of a strongly radioactive metal.

21. An electrical discharge device comprising a metallic electrode containing a polonium alloy j near the discharge portion of said device.

" t 22. An electrode for electrical discharge de lvices, said electrode having associated therewith ramalloy of a., strongly radioactive metal.

2 3. An velectrode vfor electrical 4discharge alpha particle emission from the polonium long'y 1 l strongly radioactive metal, -whereby ,the1 alpha izes the surrounding gaseous medium.

' .24. An electrode tor electrical discharge v through a gaseous medium, said electrode hav s ing llpolonium lassociated therewith, whereby the izes the surrounding gaseous medium. A

' f JOHN'l H. DILLON. e 

